Method and device for alignment of substrates

ABSTRACT

A method for aligning and contacting a first substrate with a second substrate using a plurality of detection units and a corresponding device for alignment and contact.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/830,389, filed Mar. 26, 2020, which is a continuation of U.S.application Ser. No. 16/323,539, filed Feb. 6, 2019 now U.S. Pat. No.10,692,747, issued on Jun. 23, 2020), which is a U.S. National StageApplication of International Application No. PCT/EP2016/070289, filedAug. 29, 2016, said patent applications hereby fully incorporated hereinby reference.

FIELD OF THE INVENTION

The invention relates to a method for aligning and contacting a firstsubstrate with a second substrate and a corresponding device.

BACKGROUND OF THE INVENTION

In the semiconductor industry, alignment equipment (aligners) is used toalign substrates, in particular wafers, with one another, in order tojoin them together in a further process step. The joining process iscalled bonding.

Alignment processes in which alignment markings are present on thesubstrate surfaces to be bonded are referred to as face-to-facealignments.

Inasmuch as the substrates are not transparent for the electromagneticradiation that is used to measure the substrates in order to enable adetection and/or determination of the position and orientation of thealignment markings from the external substrates surfaces facing awayfrom the substrates surfaces to be bonded, alignment markings aredetected with image detection means between the substrates before thesubstrates are brought towards one another.

This had various drawbacks, in particular particle contamination by thecamera and a large distance between the substrates to allow thepositioning of the camera between two substrates for the detection.Alignment errors during the mutual approach arise from this.

An improvement of the face-to-face alignment is represented by thealignment equipment of publication U.S. Pat. No. 6,214,692B1, which canbe regarded as the closest prior art. In the case of the latter, twogroups of lenses are used with in each case two lenses lying oppositeeach other, in order to create a system with two reference points inrelation to which the substrates are mutually positioned. The referencepoints are points of intersection of the optical axes of two lenseslying opposite one another.

The problem with the prior art includes the fact that the increasingdemands made on alignment accuracy can no longer be met by the disclosedopen, controlled methods.

Publication U.S. Pat. No. 6,214,692B1 is based on the comparison and theposition correction of two images of alignment markings. The position ofalignment markings on the two substrates arranged face-to-face isdetected individually by means of a camera system. A positioning table(substrate holder and stage) is actuated from a calculated relativeorientation and relative position of the alignment markings in such away that the incorrect position is corrected. The positioning tablecomprises guide transducers and incremental path transducers positionedclose to the drive.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a device and amethod for the alignment and contacting of substrates, with which a moreprecise and more efficient alignment and contacting of the substrates isenabled.

This problem is solved with the features of the independent claim(s).Advantageous developments of the invention are given in the sub-claims.All combinations of at least two features given in the description, theclaims and/or the figures also fall within the scope of the invention.In stated value ranges, values lying inside the stated limits are alsodeemed to be disclosed as limiting values and can be claimed in anycombination.

The invention is based on the idea of also carrying out a detection ofan additional (in particular third) alignment marking prior to analignment, said additional marking being provided either on one of thesubstrates to be aligned or on the substrate holder. In particular, theadditional alignment marking is not arranged on the contact faces of thesubstrates. The additional alignment marking is preferably arranged on aside of the substrate or the substrate holder facing away from thecontact face or arranged parallel with the contact face.

The alignment of the substrates with one another takes place inparticular indirectly on the basis of alignment markings which arelocated on contact faces of the substrates. The alignment markings onmutually opposite sides of the substrates lying opposite one another arein particular complementary to one another. Alignment markings can beany objects that can be aligned with one another, such as crosses,circles or squares or propeller-like shapes or grid structures, and inparticular phase grids for the spatial frequency domain.

The alignment markings are preferably detected by means ofelectromagnetic radiation of specific wavelength and/or wavelengthranges. At present, the latter include infrared radiation, visible lightor ultraviolet radiation. The use of radiation of shorter wavelengthsuch as EUV or x-rays is however also possible.

An—in particular independent—aspect of the present invention is that thealignment takes place, in particular exclusively, by means of thedetection of the additional alignment marking. Exclusively is understoodto mean that the other (in particular the first and second) alignmentmarkings are not or cannot be detected during the alignment.

According to an advantageous embodiment of the invention, the firstsubstrate and the second substrate are arranged between the firstsubstrate holder and the second substrate holder with a spacing Abetween the first contact face and the second contact face in aZ-direction. Spacing A amounts in particular to less than 500 microns,particularly preferably less than 100 microns, in the optimum case lessthan 50 microns, in the ideal case less than 10 microns.

The method according to the invention is in particular a method for theface-to-face alignment of at least two substrates with an arbitraryelectromagnetic radiation, in particular with UV light, more preferablywith infrared light, most preferably with visible light and/orsequential enabling of optical paths for the observation of the firstand second alignment markings, wherein a supplementation with at leastone additional optical path for the precise reproduction of thesubstrate and substrate holder position is provided, which additionaloptical path is not arranged or does not run between the substratesduring the alignment of the substrates, but rather enables a detectionfrom outside.

The method according to the invention increases the alignment accuracyin particular by means of additional X-Y position and/or orientationinformation, which is detected with additionally provided detectionunits and/or measurement and control systems and used for controllingthe alignment.

For this purpose, the device according to the invention comprises an inparticular software-assisted control unit, by means of which the stepsand components described here are controlled. According to theinvention, closed control circuits and controls are understood to beincluded in the control unit.

X- and Y-direction or X- and Y-position are understood to meandirections or positions arranged in an X-Y coordinate system orrespectively in an arbitrary Z-plane of the X-Y coordinate system. TheZ-direction is arranged orthogonal to the X-Y direction.

The X- and Y-direction corresponds in particular to a lateral direction.

Position features are derived/calculated from the position and/ororientation values of the alignment markings of the substrates and fromalignment markings on the substrate holder.

According to the invention, at least one additional position feature isin particular detected with at least one additional measurement systemwith a new, additional optical path. The at least one additionalalignment marking is preferably located in the spatial proximity of thealignment markings of the substrates.

The method according to the invention and the device according to theinvention thus comprise in particular at least one additionalmeasurement and/or control system, wherein the alignment accuracy isincreased by additional measured values and correlations with at leastone of the measured values of the other detection units. By means of acorrelation of at least one of the measured alignment markings in thebond interface between the contact faces with an the alignment markingalso visible when the substrates are aligned, the direct observabilityof an alignment mark and therefore a real-time measurement and controlduring the alignment is enabled. The alignment accuracy of thesubstrates thus increases.

The additional alignment marking is in particular arranged on the rearside of the substrate holder.

An unequivocal correlation is in particular produced between theadditionally added position feature on the substrate holder and theposition features on the substrates, said correlation preferably notbeing changed up to and during the alignment.

As a result of the additionally added position features on the substrateholder, which are correlated unequivocally with the position features onthe substrate, a direct observation of the position features on thesubstrate can be replaced by a direct observation of the positionfeatures on the substrate holder. This has the advantage that theobservable part of the substrate holder can virtually always be arrangedin the field of view or measurement range of the additional measurementsystem.

An active feedback of the data for the positioning and positioncorrection increases the accuracy compared to a controlled positioningin the prior art, since a control option of the actual status of theposition is provided in closed control circuits. In particular, apredefined distance with a given number of increments is not thereforetravelled, but rather the distance already travelled is measured, sothat a comparison between setpoint and actual can be made, in particularwith regard to speeds and/or accelerations. The aim of the invention isto increase the accuracy of the alignment of two substrates using amethod with which the alignment can be observed in real-time, inparticular from outside the bond interface. The substrates are arrangedin particular with a minimum spacing from one another and no item ofequipment is preferably located between the substrates.

The core idea of the invention is in particular the introduction of atleast one additional measurement and control system and the linking ofthe existing measured values with the additional, newly detectedposition and/or orientation values. As a result of the correlation ofthe measured alignment markings in the bond interface with an alignmentmarking on the substrate holder, in particular on its rear side, and/orthe substrate, in particular at its rear side, which can be detected,preferably directly, during the alignment, the direct observability ofthe additional alignment marking and a real-time measurement and controlis enabled. The alignment accuracy is improved by this measure.

During the detection of the first alignment marking, the secondsubstrate and the second substrate holder are moved in an X-Y directionout of the optical axis of the first detection unit, in order to enablea detection.

During the detection of the second alignment marking, the firstsubstrate and the first substrate holder are moved in an X-Y directionout of the optical axis of the second detection unit, in order to enablea detection.

Device

The device according to the invention for the alignment of at least twosubstrates comprises at least one optical system, comprising two lensesor detection units, in particular aligned with one another, the opticalpaths of which preferably meet in a common focal point.

According to an advantageous embodiment, the optical system comprisesbeam-forming and/or deflection elements such as mirrors, lenses, prisms,radiation sources in particular for Köhler illumination and imagedetection means such as cameras (CMOS sensors, or CCD, or area or lineor point detection means such as a phototransistor) and movement meansfor focusing and evaluation means for controlling the optical system.

In an embodiment of the device according to the invention, an opticalsystem and a rotation system are used for the substrate positioningaccording to the principle of the turn-over adjustment, see in thisregard Hansen, Friedrich: Justierung, VEB Verlag Technik, 1964, para.6.2.4, Umschlagmethode, wherein at least one measurement is carried outin a defined position and at least one measurement is carried out in aturned-over, oppositely orientated position rotated through 180 degrees.The measurement result thus obtained is in particular free fromeccentricity errors.

A development of the device according to the invention comprises two, inparticular identical, structurally identical optical systems with lensesaligned with one another and fixable relative to one another.

An inventive development of the device comprises more than two identicaloptical systems with aligned lenses.

Furthermore, a device according to the invention comprises substrateholders for holding the substrates to be aligned.

In a further embodiment of the device according to the invention, atleast one substrate holder is used which is at least partially,preferably over 95%, transparent at defined points for the in particularsimultaneous observation of the two substrate sides.

In a further embodiment of the device according to the invention, atleast one substrate holder is used, which comprises openings and/orapertures and/or inspection windows at defined points for the inparticular simultaneous observation of the two substrates sides.

Furthermore, the device according to the invention can comprise a systemfor producing pre-bonds.

Furthermore, a device according to the invention preferably comprisesmovement devices with drive systems, guide systems, holding fixtures andmeasurement systems, in order to move, to position and to align with oneanother the optical systems and the substrate holders and/or substrates.

The movement devices can generate each movement as a result ofindividual movements, so that the movement devices can preferablycomprise rapid rough-positioning devices not meeting the accuracyrequirements as well as precisely operating fine-positioning devices.

A setpoint value for the position to be approached is an ideal value.The movement device moves near to the ideal value. Reaching a definedarea around the ideal value can be understood to mean reaching thesetpoint value.

A rough-positioning device is understood to mean a positioning devicewhen the approach and/or repetition accuracy diverges from the setpointvalue by more than 0.1%, preferably more than 0.05%, particularlypreferably more than 0.01%, related to the total travel path or rotationrange, in the case of rotating rotational drives related to a fullrevolution of 360 degrees.

With a rough-positioning device, for example, an approach accuracy of600 mm*0.01% thus results with a travel path of over 600 mm, i.e. morethan 60 microns as residual uncertainty. In other embodiments ofrough-positioning, the residual uncertainty of the approach orrepetition accuracy is less than 100 microns, preferably less than 50microns, particularly preferably less than 10 microns. Thermalinterference variables should preferably also be taken into account.

A rough-positioning device performs the positioning task with sufficientaccuracy only if the difference between the actual position in factreached and the setpoint value of the position lies within the travelrange of an assigned fine-positioning device.

An alternative rough-positioning device performs the positioning taskwith sufficient accuracy in particular only if the difference betweenthe actual position in fact reached and the setpoint value of theposition lies within half the travel range of an assignedfine-positioning device.

A fine-positioning device is understood to be a positioning device whenthe residual uncertainty of the approach and/or repetition accuracy fromthe setpoint value does not exceed less than 500 ppb, preferably lessthan 100 ppb, in the ideal case 1 ppb related to the total travel pathor rotation range.

The fine-positioning device according to the invention will preferablyhave an absolute positioning error less than 5 microns, preferably lessthan 1 micron, particularly preferably less than 100 nm, veryparticularly preferably less than 10 nm, in the optimum case less than 5nm, in the ideal case less than 1 nm.

The present device and the associated processes comprise at least twopositioning devices having extremely high precision and reproducibility.A concept of mutual error corrections can be used for the quality of thealignment of the substrates. Thus, with a known misalignment (warpingand/or displacement) of a substrate and, corresponding thereto, of thepositioning device, the alignment accuracy can be increased with theadjustment and correction of the position of the other positioningdevice and the other substrate with correction values or correctionvectors. It is a question here of the magnitude and nature of thewarping and/or displacement as to how the control or regulation usesrough and fine positioning or only rough positioning or only finepositioning for the error correction.

In the subsequent text, positioning devices (rough or fine or combinedpositioning devices) and alignment means are regarded and used assynonyms.

According to the invention, the alignment of the substrates with oneanother can take place in all six degrees of freedom of movement: threetranslations according to the coordinate directions x, y and z and threerotations about the coordinate directions. According to the invention,the movements can be carried out in any direction and orientation. Thealignment of the substrates in particular comprises a passive or activewedge error compensation, preferably according to the disclosure inpublication EP2612109B1.

Robots for substrate handling are included as movement devices. Theholding fixtures can be integrated as components or integrated asfunctions in the movement devices.

Furthermore, a device according to the invention preferably comprisescontrol systems and/or evaluation systems, in particular computers, inorder to carry out the described steps, in particular movementsequences, to carry out corrections, to analyse and store operationalstatuses of the device according to the invention.

Processes are preferably created as formulas and executed in amachine-readable form. Formulas are optimized compilations of values ofparameters, which are connected in a functional or process-relatedmanner. The use of formulas makes it possible to ensure reproducibilityof the production sequences.

Furthermore, a device according to the invention according to anadvantageous embodiment comprises supply and/or auxiliary and/orsupplementary systems (compressed air, vacuum, electrical energy,liquids such as hydraulics, coolants, heating agents, means and/ordevices for temperature stabilisation, electromagnetic shielding).

Furthermore, the device according to the invention comprises frames,claddings, vibration-suppressing or -damping or -absorbing active orpassive subsystems.

Measurement

Furthermore, a device according to the invention comprises at least onemeasurement system, preferably with measurement units for each movementaxis, which can be constituted in particular as displacement measuringsystems and/or angle measuring systems.

Both tactile, i.e. touch, or non-tactile measurement methods can beused. The standard measure, the unit of the measurement, can be presentas a physical-material object, in particular as a scale, or can beimplicitly present in the measurement process, such as the wavelength ofthe radiation used.

At least one measurement system can be selected and used for theachievement of the alignment accuracy. Measurement systems implementmeasurement methods. In particular, use can be made up of

inductive methods and/or

capacitive methods and/or

resistive methods and/or

comparison methods, in particular optical image recognition methodsand/or

incremental or absolute methods (with in particular glass

standard measures as a scale, or interferometers, in particular laserinterferometers, or with a magnetic standard measure) and/or

travel-time measurements (Doppler method, time-of-flight method) orother time recording methods and/or

triangulation methods, in particular laser triangulation,

autofocusing methods and/or

intensity measurement methods such as fibre-optic telemeters.

Additional Measurement System with Variations, Substrate Holder

Furthermore, a particularly preferred embodiment of the device accordingto the invention comprises at least one additional measurement system,which detects the X-Y position and/or alignment orientation and/orangular position of at least one of the substrates and/or one of thesubstrate holders in relation to a defined reference, in particular tothe frame. A part made in particular of natural hard stone or mineralcast iron or spheroidal graphite cast iron or hydraulically boundconcrete can be provided as a frame, said part being in particularvibration-damped and/or vibration-insulated and/or provided withvibration absorption.

According to the invention, measured values can be combined with oneanother and/or referenced to and/or correlated with one another, sothat, from a measurement of one alignment marking, conclusions can bedrawn as to the position of the other alignment marking related thereto.

In an embodiment according to the invention, the position of a substrateholder is detected at a point (or position or measurement spot or fieldof view) in relation to the reference, in particular the first alignmentmarking on a first substrate and/or the second alignment marking on thesecond substrate.

In a further embodiment according to the invention, the position of asubstrate holder is detected at precisely two points in relation to thereference.

In a further embodiment according to the invention, the position of asubstrate holder is detected at precisely three points in relation tothe reference and the position and orientation of the substrate holderare thus determined.

In a first embodiment according to the invention, optical patternrecognition by means of camera systems and patterns applied on thesubstrate holder can be used for a position determination at a point orat two points or three points or an arbitrary number of points. Thepatterns are detected in a real-time system, in particular continuouslyduring the alignment. The listed measurement methods can also be usedfor the position determination.

A reversal is conceivable according to the invention, in particular bythe provision of the detection units on the substrate holder and theprovision of alignment markings on the frame.

In order that a detection, evaluation and control can take place at anarbitrary time, in particular continuously, the patterns are distributedaccording to an advantageous embodiment over a larger area than thefield of view of an image detection system of the detection units, inorder to provide the control unit (and/or regulating unit) with measuredvalues, in particular continuously.

In a further inventive embodiment of the device, at least one of thesubstrate holders comprises a through-opening for the detection of thealignment markings from the support side of the substrates.

According to the invention, it is advantageous if at least one of thesubstrates comprises at least one alignment marking on the surface to bebonded (contact face) and at least one alignment marking on theopposite-lying surface (support face).

The alignment markings are preferably a plurality of alignment marksdistributed, preferably uniformly, in particular unequivocallyassignable, on the support face of at least one of the substrates. Thealignment marking on the support face can be correlated at least inrelation to its X-Y position and/or alignment orientation with the X-Yposition and/or alignment orientation of the alignment marking of thesame substrate. This enables a continuous position determination duringthe loading and alignment of the substrates up to the substrates makingcontact.

In a development of the present invention, the alignment marks on thesupport face are distributed, in particular uniformly, up to an edgezone (edge exclusion zone) of the substrate.

In a further embodiment of at least one of the substrates, the alignmentmarks on the support face are distributed one-to-one with respect to thecontact face of the same substrate and the alignment marking arranged onthe contact face.

In a further embodiment according to the invention, at least oneinterferometer with a suitably constituted, in particular monolithic,reflector for the detection of the X-Y position and/or the orientationdetermination of the substrate holder can be used for an X-Y positiondetermination at at least one point. The number of interferometers is inparticular equal to the number of reflection faces of the reflector.

The substrate holder, in particular formed from a monolithic block,preferably comprises at least two of the following functions:

substrate fixing by means of vacuum (vacuum tracks, connections),

shape compensation for the deformation of the substrate by means ofmechanical and/or hydraulic and/or piezoelectronic and/or pyroelectricaland/or electrothermal actuation elements, particularly preferablyaccording to embodiments EP2656378B1, WO02014191033A1,

position and/or orientation determination (standard measures, reflectionfaces and/or prisms, in particular reflectors for interferometry,register marks and/or register mark fields, two-dimensionallyconstituted standard measures for planes, volume standard measures, inparticular steps)

movement (guide tracks)

Movement devices according to the invention that are not used for thefine adjustment are in particular constituted as robot systems,preferably with incremental displacement sensors. The accuracy of thesemovements devices for auxiliary movements is decoupled from the accuracyfor the alignment of the substrate stack, so that the auxiliarymovements are performed with lower repetition accuracy of less than 1mm, preferably less than 500 microns, particularly preferably less than150 microns.

The control and/or regulating of movement devices according to theinvention for the (lateral) alignment (fine adjustment) is in particularcarried out on the basis of X-Y positions and/or alignment orientationsdetected with other measurement means. The accuracy of these movementsdevices is preferably less than 200 nm, preferably less than 100 nm,particularly preferably less than 50 nm, very particularly preferablyless than 20 nm, in the optimum case less than 10 nm, in the ideal caseless than 1 nm.

Method

A first embodiment of an alignment method according to the inventioncomprises the following, in particular at least partially sequentialand/or simultaneous steps, in particular the following sequence:

First process step: The first/lower substrate is loaded with a supportface on the first/lower substrate holder, wherein a first alignmentmarking is provided (present) on the opposite side (contact face).

Second process step: The first/lower substrate moves with the substrateholder into the field of view of a detection position of a first/upperdetection device, in particular using movement devices for the roughadjustment.

Third process step: The optical system travels to the detectionposition, if this has not already been done by the second process step.Optionally, a self-calibration of the optical system can already takeplace at this time or before the initiation of the movement of thedetection position.

Fourth process step: The first/upper detection device is focused ontothe pattern of the first alignment marking to be detected, said patternbeing arranged on the contact face of the substrate to be bonded.

Optionally, the optical system can adjust the second/lower detectionunit onto the focus plane of the first/upper detection unit.

Fifth process step: Detection of the first alignment marking, inparticular by means of pattern recognition. At the same time, inparticular by synchronisation with the first detection unit, the X-Yposition and/or alignment orientation of the first substrate holderand/or the first substrate is detected, preferably at a face other thanthe contact face, by an additional measuring system according to theinvention (with a third detection unit).

Sixth process step: Clamping, in particular mechanically and/orelectronically and/or magnetically, of the position of the opticalsystem, in particular by reducing all the degrees of freedom to zero.

Seventh process step: The optical system adjusts the second/lowerdetection unit onto the focal plane of the first/upper detection unit.

Optionally, the adjustment has been carried out following the fourthprocess step and is not required.

Eighth process step: A control and evaluation computer (in particular inthe control unit) performs abstractions and/or calculations in order toobtain measurement results for controlling the alignment: The controland evaluation computer in particular creates a correlation of themeasurement results of the optical system and of the additional (third)measurement system and stores the results, in particular as a setpointvalue of the X-Y position and/or an alignment orientation of thefirst/lower substrate holder and of the first/lower substrate.

Ninth process step: The first/lower substrate holder is moved out of thefield of view (beam path for the detection) of the optical system.Blocking of the optical path for the first detection unit is thusremoved. The optical system preferably continues to remain fixed.

Tenth process step: The second/upper substrate is loaded onto thesecond/upper substrate holder. This process step can already be carriedout before one of the preceding process steps.

Eleventh process step: The second/upper substrate holder moves with thesecond/upper substrate into the field of view of the optical system.

Twelfth process step: The second/lower detection unit of the opticalsystem seeks and detects, analogous to the first/upper detection unit,the alignment marking on the second/upper substrate. The optical systemis not thereby moved mechanically, although a correction of the focusingis conceivable. Preferably, however, a focusing movement is not carriedout either.

Thirteenth process step: The second/upper substrate and the second/uppersubstrate holder block the optical path of the first/upper detectionunit, so that no direct observability/detection of the contact face ofthe first/lower substrate to be bonded is possible in the alignedposition.

Fourteenth process step: The control and evaluation computer ascertainsthe alignment errors, regarding which reference is made to thedisclosures in publications U.S. Pat. No. 6,214,692B1, WO2014202106A1.In particular, an alignment error vector is created from the alignmenterror. In particular, at least one correction vector is then calculated.The correction vector can be a vector parallel to the alignment errorvector and opposite to it, so that the sum of the alignment error vectorand the correction vector produces zero. In special cases, furtherparameters can be taken into account in the calculation of thecorrection vector, so that the result is different from zero.

Fifteenth process step: The X-Y position and the alignment orientationof the second/upper substrate (together with the substrate holder) areadjusted according to the correction vector and then clamped, so thatthe calculated alignment error is at least minimised, preferablyeliminated.

Sixteenth process step: After the clamping/fixing of the second/uppersubstrate has taken place, the X-Y position of the second uppersubstrate is again detected/checked with the second/lower detectionunit. Displacements and/or warping, which had been caused by theclamping, can thus be detected and minimised, in particular eliminated,by iteration of the twelfth to the fifteenth process step.

Alternatively, the detected displacements and/or warping can be takeninto account to create correction values and/or correction vectors, sothat an elimination can be taken into account in the subsequent processsteps. The correction values for the displacements are preferably lessthan 5 microns, preferably less to the 1 micron, particularly preferablyless than 100 nanometres, very particularly preferably less than 10nanometres, in the optimum case less than 5 nanometres, in the idealcase less than 1 nanometer. The correction values for warping are inparticular less than 50 micro-radians, preferably less than 10micro-radians, particularly preferably less than 5 micro-radians, veryparticularly preferably less than 1 micro-radian, in the optimum caseless than 0.1 micro-radians, in the ideal case less than 0.05micro-radians.

In the fifteenth process step, analogous to the twelfth process step, atleast one measurement of the position can take place before and at leastone measurement after the fixing of the upper substrate. An iterativecorrection of the errors is conceivable according to the invention, sothat the next process steps are only carried out after meeting a definedaccuracy requirement (threshold value).

Sixteenth process step: The first/lower substrate holder moves back intothe already detected position and orientation of the setpoint value (seeeighth process step). The X-Y position and the alignment orientation ofthe lower substrate holder (together with substrate) are checked withthe additional measurement system, in particular in real-time. Theobservability of the first alignment marking of the first substrate isnot provided, since the clamped upper substrate holder blocks theoptical path.

Seventeenth process step: The actual X-Y position and the alignmentorientation of the first/lower substrate holder are corrected until suchtime as the difference from the setpoint value is zero, but at least adefined threshold value is not fallen below.

Eighteenth, optional process step: The substrates are joined, regardingwhich reference is made to the disclosure of publication WO2014191033A1.

Nineteenth process step: The substrate stack is unloaded from thedevice.

A second, alternative embodiment of the alignment method according tothe invention comprises the following changes to the loading sequencesfor the upper and lower substrate as compared to the first embodiment:

As a first process step according to the invention, the first/lowersubstrate is loaded on the first/lower substrate holder.

As a second process step according to the invention, the second/uppersubstrate is loaded onto the second/upper substrate holder.

The process steps of the first embodiment then apply analogously.

In a third embodiment of the method according to the invention, thefirst and/or second method is changed in that the directions above andbelow are interchanged both in the device according to the invention andalso in the method. In particular, the upper substrate holder is thusobserved with at least one additional measurement system.

In a fourth embodiment of the method according to the invention, thelisted processes are changed in that the loading sequence of thesubstrates is interchanged with the process result remaining the same.

In a fifth embodiment of the method according to the invention,speeding-up is achieved by parallelising the process steps, inparticular the loading of the second substrate is already carried outduring a pattern recognition step on the first substrate.

In a sixth embodiment of the method and associated device according tothe invention, the additional measurement systems can detect theposition and/or orientation both of the upper and also the lowersubstrate holder and/or the upper and also the lower substrate.

In a seventh embodiment of the method and associated device according tothe invention, the additional measurement systems can detect theposition and/or orientation of the upper substrate holder and/or theupper substrate.

All technically possible combinations and/or permutations andduplications of the functional and/or material parts of the device andthe accompanying changes in at least one of the process steps orprocesses are deemed to be disclosed.

Insofar as device features are disclosed in the present text and/or inthe subsequent description of the figures, these are also deemed to bedisclosed as method features and vice versa.

Further advantages, features and details of the invention emerge fromthe following description of preferred examples of embodiment and on thebasis of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagrammatic cross-sectional representation of a firstembodiment of the device according to the invention,

FIG. 2a shows a diagrammatic, enlarged cross-sectional representation ofthe embodiment according to FIG. 1a in a first process step,

FIG. 2b shows a diagrammatic, enlarged cross-sectional representation ofthe embodiment according to FIG. 1a in a second process step.

FIG. 2c shows a diagrammatic, enlarged cross-sectional representation ofthe embodiment according to FIG. 1a in a third process step.

Advantages and features of the invention are marked in the figures withreference numbers each identifying the latter according to embodimentsof the invention, wherein components or features with an identical oridentically acting function are marked with identical reference numbers.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a diagrammatic functional representation (not true toscale) of the main components of a first embodiment of an alignmentapparatus 1. Alignment apparatus 1 is capable of aligning substrates 16(denoted as the first and/or lower substrate), 17 (denoted as the secondand/or upper substrate) and/or substrate stacks with one another, saidsubstrates not being shown in FIG. 1, and/or of joining the lattertogether at least partially and/or provisionally (so-called pre-bond).Possible movements/degrees of freedom of the functional componentsdescribed below are represented symbolically by arrows.

First substrate 16 is loaded onto a first substrate holder 10 and can befixed on the latter with no remaining degrees of freedom of substrate 16relative to first substrate holder 10. Second substrate 17 is loadedonto a second substrate holder 13 and can be fixed on the latter with noremaining degrees of freedom of substrate 17 relative to secondsubstrate holder 13.

First, in particular lower, substrate holder 10 is arranged on a firstmovement device 11 for holding and implementing feed and adjustmentmovements (alignment) of first substrate holder 10.

Second, in particular upper, substrate holder 13 is arranged on a secondmovement device 14 for holding and implementing feed and adjustmentmovements (alignment) of second substrate holder 13. Movement devices11, 14 are in particular fixed to a common, solid table or frame 9, inorder to reduce/minimise vibrations of all functional components.

For the observation (detection) of a first alignment marking 20 and asecond alignment marking 21, there is an optical system 2 comprising:

-   -   a first detection unit 3, in particular an image detection        means, for detecting first alignment marking 20 on first        substrate 16 and    -   a second detection unit 4, in particular an image detection        means, for detecting the second alignment marking on second        substrate 17.

Optical system 2 can be focused onto a preferably common focal plane 12,which is located between first and second substrate 16, 17, when thelatter are arranged for alignment. Movements of the optical system 2, inparticular in the X-, Y- and Z-direction, are carried out by means of apositioning device 5 for positioning optical system 2. Positioningdevice 5 is in particular fixed to the solid table or frame.

In a particularly preferred embodiment, not represented, entire opticalsystem 2 (with positioning means 5, detection units 3 and 4, etc.) isused in a twofold, mirror-symmetrical embodiment.

At least one additional, in particular optical, measurement system 6with at least a third detection unit 7 of additional measurement system6 is used for the inventive increase in the alignment accuracy by thedetection of a third alignment marking 22. A movement of the additionalmeasurement system is carried out with a positioning device 8.

Insofar as an optical measurement system 6 is involved, positioningdevice 8 can carry out focusing with regard to third alignment marking22 by moving third detection unit 7 in the Z-direction. A positioning inthe X-Y direction is also conceivable, wherein in particular fixing ofmeasurement system 6, preferably to the table/frame, takes place duringthe alignment. Alternatively, the exact X-Y position of measurementsystem 8 must be known.

In the represented inventive embodiment of alignment apparatus 1, theX-Y position and/or orientation (in particular also the rotationorientation) of lower substrate holder 10 is in particular detected withparticularly high accuracy by means of additional measurement system 6.

In a further inventive embodiment of alignment apparatus 1, notrepresented, the position and/or orientation of the upper substrateholder is in particular detected with particularly high accuracy bymeans of the additional measurement system.

In a further inventive embodiment of alignment apparatus 1, notrepresented, the positions and/or orientations of the upper substrateholder and the lower substrate holder are in particular detected withparticularly high accuracy by means of the additional measurementsystem.

In a further inventive embodiment of the alignment apparatus, notrepresented, the position and/or orientation of at least one of thesubstrates is in particular detected with particularly high accuracy bymeans of at least one measurement system. For this purpose, thealignment markings on the contact face and the markings on the sidefacing away from the contact face are detected.

FIG. 2a shows a diagrammatic representation of a process step accordingto the invention for assigning measured values of at least two detectionunits to one another, in particular two detection units for detecting atleast two X-Y positions of alignment markings 20, 22 arranged ondifferent sides of the first substrate 16 and/or first substrate holder10.

First/lower substrate 16 is fixed on the first fixing face 10 of firstsubstrate holder 10. As a fixing, use is made in particular ofmechanical and/or electrostatic clamping, a pressing force, which isgenerated due to a pressure difference between the surroundings innormal atmosphere and the underpressure at first substrate holder 10,also referred to as a vacuum fixing. The fixing takes place inparticular in such a way that first substrate 16 does not experience anyparasitic or undesired movement relative to first substrate holder 10throughout the entire method according to the invention; in particular,thermal expansion can be prevented or reduced, insofar as firstsubstrate holder 10 and first substrate 16 each have a correspondingthermal expansion coefficient, preferably running in a linearlycorresponding manner, wherein the difference in the thermal expansioncoefficients and/or the linear course of the thermal expansioncoefficients preferably amounts to less than 5%, preferably less than3%, particularly preferably less than 1%.

The apparatus is preferably operated in a temperature-stabilisedenvironment, in particular in a clean room, in which a temperaturevariation of less than 0.5 Kelvin, preferably less than 0.1 Kelvin,particularly preferably 0.05 Kelvin, in the optimum case less than 0.01Kelvin can be complied with during an alignment cycle.

Fixed first substrate 16 and first substrate holder 10 can be understoodto be a quasi-monolithic body for the performance of the movements offirst substrate 16, which permit no relative movements with respect toone another.

This substrate fixing can take place in a form-fit and/or preferably ina friction-locked manner. The effect of a quasi-monolithic connection isthat influences which could bring about a displacement and/or warpingand/or deformation between the substrate holder and the substrate are atleast reduced, preferably reduced at least by an order of magnitude,particularly preferably eliminated. The influences may be thermal,and/or mechanical, and/or flow-related and/or of a material nature(particles).

With a form-fit or friction-locked connection, the substrate can beconnected to the substrate holder in such a way that the difference in athermal expansion can in particular be prevented. Furthermore, theindependent deformation of the substrate can be reduced, eliminatedand/or corrected with the substrate holder, regarding which reference ismade to the disclosure of EP2656378B1.

During the detection of first alignment marking 20, first substrateholder 10 is located in an optical path of first (upper) detection unit3. First alignment marking 20 is arranged on contact face 16 i of firstsubstrate 16 to the bonded in the field of view, in particular in theoptical path, of first (upper) detection unit 3. First detection unit 3generates an in particular digital image, which is represented herediagrammatically as an alignment mark in the form of a cross. Firstalignment marking 20 can also comprise a plurality of alignmentmarkings. A measured value is generated/calculated from the image of thealignment mark, said measured value characterising in particular the X-Yposition and/or alignment orientation (in particular in the rotationdirection about a Z-direction), i.e. the alignment state of firstsubstrate 16.

During the detection of first alignment marking 20, second/lowerdetection unit 4 preferably delivers no measured value, especially sincesecond substrate 17 is/has been arranged outside the optical path offirst detection unit 3.

First/lower substrate holder 10 and/or first/lower substrate 16 comprisethird alignment marking 22, with the aid of which the X-Y positionand/or alignment orientation (in particular in the rotation directionabout a Z-direction), i.e. the alignment state of substrate holder 10and/or of first substrate 16, are detected in particular from anotherdirection, preferably a direction lying diametrically opposite the firstdetection in the Z-direction.

A relative movement of first detection unit 3 towards the detection unit7 can preferably be measured, more preferably no relative movementbetween first detection unit 3 and third detection unit 7 is carried outfrom the detection of first alignment marking 20 and third alignmentmarking 22 up to contacting of first and second substrate 16, 17.

Third (additional) detection unit 7 of additional measurement system 6delivers a measured value of the X-Y position and/or orientation offirst/lower substrate holder 10 from the measurement of the thirdalignment marking 22 of first/lower substrate holder 10. The measuredvalue is in particular generated from a preferably digital image, whichis represented symbolically as a cross. Third alignment marking 22 canalso comprise a plurality of alignment markings.

The two measured values (X-Y position and/or alignment orientation offirst alignment marking 20 of first substrate 16 and the X-Y positionand/or alignment orientation of third alignment marking 22 of firstsubstrate holder 10 or first substrate 16) are assigned to one anotherand/or correlated with one another, so that the X-Y position and/oralignment orientation of first alignment marking 20 can at all times beassigned one-to-one to the third alignment marking on the basis of theX-Y position and/or alignment orientation, in particular by detection ofthe X-Y position and/or alignment orientation.

By means of this process step, an alignment can be carried out withoutdirect detection of the X-Y positions and/or alignment orientations offirst alignment marking 20 and/or of second alignment marking 21 duringthe alignment and/or contacting of first substrate 16 with secondsubstrate 17. Furthermore, the spacing between the substrates during thealignment can be minimised. The spacing can preferably alreadycorrespond to the spacing of the substrates during the detection of thefirst and second alignment markings.

In other words, an obstacle-free optical path between substrate holder10 and additional measurement system 6 can in particular be provided,with which the alignment of the substrates can be or is undertaken in acontrol circuit. By means of this process step, the X-Y position and/oralignment orientation of first substrate holder 10 and therefore of thefirst substrate fixed on first substrate holder 10 can be preciselydetermined and re-established in a reproducible manner.

The re-establishment of the X-Y position and/or the alignmentorientation in particular of substrate holder 10 and in particular thesubstrate monolithically connected thereto represents an, in particular,independent core aspect. The process steps for this have already beendiscussed elsewhere.

In particular, a repetition accuracy of the positioning (measured as arelative alignment error between the two substrates), also known as areverse play, of less than 1 micron, preferably less than 100 nm,particularly preferably less than 30 nm, very particularly preferablyless than 10 nm, in the optimum case less than 5 nm, in the ideal caseless than 1 nm is achieved. The reverse play can also be the repeatedapproach of a given position with the aid of movement devices 11, 14and/or 5, 8. The reverse play results from the movements of the movementdevices, only the detection location varies, so that the measuredmagnitude exists as a relative alignment error. A positioning accuracyof a movement device that does not have any effect on the substrates canbe regarded as a non-relevant reverse play.

According to the invention, it is preferable, for a further increase inthe alignment accuracy, to operate first detection unit 3 in atime-synchronized manner with third detection unit 7, in particular witha time difference of the detections of the measured values of less than1 tenth of a second, preferably less than 1 millisecond, particularlypreferably less than 10 microseconds, very particularly preferably lessthan 1 microsecond, in the optimum case less than 1 ns, in the idealcase 0.0 ns. This is particularly advantageous, because the effect ofinterfering influences such as mechanical vibrations can be eliminated.Mechanical vibrations propagate, amongst other things with astructure-borne noise, at several thousand m/s in materials. If acontrol and the detection means operate more quickly than thepropagation speed of the structure-borne noise, a disruption is reducedor eliminated.

If a disruption changes the orientation of first substrate 16 on firstsubstrate holder 10 in such a way that first detection unit 3 hasalready recorded a measured value and additional measurement system 6with detection unit 7 has not yet recorded a measurement value, thedisruption can contribute towards a reduction in the accuracy of thealignment, because in the time between the measured values beingrecorded by detection means 3 and 7, vibration-induced, rapid mechanicalposition changes in order of magnitude of the nanometre or micron can inparticular take place. If the recording of the measured values takesplace with a time lag (of the order of seconds or minutes), furtherinterfering influences such as heat-related changes in shape and changesin length can also reduce the alignment accuracy.

If first detection unit 3 and third detection unit 7 are synchronisedwith one another (in particular by simultaneous triggering of thedetection and equalising the detection time and/or identical integrationtime for camera systems), several interfering influences can be reduced,in the optimum case eliminated, since the detection is to take place ata time when the interfering influences have the least possible effect onthe detection accuracy.

In a possible embodiment of the apparatus, the detection can take placewith known, in particular periodic interfering influences, in particularsynchronised at the peak of the oscillation. For this purpose, vibrationsensors (acceleration sensors, interferometers, vibrometers) canpreferably pick up the interfering influences beforehand at points ofthe apparatus relevant to the accuracy and, for the purpose ofelimination, process them in particular in computing units, computers.In a further embodiment, the vibration sensors can be fixedly installedat characteristic points of the apparatus.

In a further possible embodiment, the apparatus can in particular beused with a combination of active and/or passive vibration damping,active and/or passive vibration absorption and/or active and/or passivevibration isolation, also constituted in a cascaded manner. In addition,the vibrations can, as interfering influences, be superimposed withforced vibrations, so that the detection of the alignment marks can takeplace in a so-called lock-in process. For the characterization of theapparatus and for checking the vibrational states, use can be made ofmodal analyses, and/or FEM. This and the design of such apparatuses areknown to the person skilled in the art.

First and third detection units 3, 7 are clamped before or during orafter a detection of first and third alignment markings 20, 22, whereinat least the absolute and/or relative degrees of freedom in the X- andY-direction are reduced to zero. Relative is understood to mean themovement of first detection unit 3 with respect to third detection unit7.

FIG. 2b is a diagrammatic representation of a process step according tothe invention for the measured value detection of second/upper substrate17. Optical system 2 is in particular already in a clamped state and animage and/or an X-Y position of at least one alignment mark offirst/lower substrate 16 is stored (not represented). In the clampedstate, at least the absolute and/or relative degrees of freedom of thesecond detection unit are reduced to zero in the X- and Y-direction withrespect to the first detection unit.

In the clamped state, the X-Y positions and/or alignment orientations ofthe first, second and third alignment markings can be related to thesame X-Y coordinate system. Alternatively or in addition, the first,second and third detection units are calibrated on the same X-Ycoordinate system.

Second/upper substrate 17 fixed on second/upper substrate holder 13 ismoved into a detection position by means of second movement device 14for the movement of second substrate holder 13 and the X-Y positionand/or alignment orientation of second alignment marking 21 of secondsubstrate 17 is detected by means of second/lower detection unit 4.

The aim is an alignment of second substrate 17 that is as perfect aspossible with respect to the X-Y position and/or orientation offirst/lower substrate 16. Since lower substrate 16 would be an obstaclein the optical path for the observation of second alignment marking 21of second/upper substrate 17 by second detection unit 4, first/lowersubstrate 16 is moved out of the optical path, in particular by amovement in the X- and/or Y-direction, preferably without any movementin a Z-direction.

The correction of the X-Y position and the relative orientation of thetwo substrates is carried out by a comparison of the X-Y positionsand/or alignment orientations of the first and second alignment markingscorrelated to the third alignment marking.

Once the alignment state of the second/upper substrate is reached within particular a minimal, preferably eliminated, alignment error, theother substrate holder is clamped in this process step, i.e. its degreesof freedom are removed at least in the X- and Y-direction.

FIG. 2c shows a diagrammatic representation of a process step accordingto the invention for the alignment of substrate 16 with respect to the,in particular clamped, second substrate 17.

The optical path of optical system 2 is blocked during the alignmentbetween first detection unit 3 and second detection unit 4 by firstsubstrate holder 10 and second substrate holder 13, so that detectionunits 3, 4 cannot be used during the alignment.

Additional measurement system 6 with third detection unit 7, which in aparticularly preferred embodiment is a camera system with a microscope,generates, preferably in real-time, in particular continuously, imagedata which can be used as raw data for an X-Y position and/ororientation control.

The (theoretical or average) spacing (in particular without takingaccount of any pretensioning or sagging) of contact faces 16 i, 17 i tobe bonded amounts in particular to less than 1 mm, preferably less than500 microns, particularly preferably less than 100 microns, in theoptimum case less than 50 microns, in the ideal case less than 10microns. In particular, the spacing can be adjusted by movement devices11 and/or 14.

In particular, a setpoint value ascertained/established according toFIG. 2a is used for the alignment of substrates 16 and 17. The setpointvalue contains in particular image data of third alignment marking 22 offirst substrate holder 10 and/or the ascertained X-Y position dataand/or alignment orientation data for movement device 11 of firstsubstrate holder 10 and/or control parameters such as path curves forthe optimum approach of the X-Y position and/or in particularmachine-readable values for the drives.

In a further embodiment, residual errors that are not eliminated in thepositioning of the upper and/or lower substrate can be taken intoaccount as correction values for the positioning of the other (lower orrespectively upper) substrate.

By means of first movement device 11, first substrate holder 10 is movedin a position- and in particular orientation-controlled manner untilsuch time as the alignment error, which is calculated from the setpointvalue of the additional measurement system and the current positionand/or orientation of the substrate holder, is minimised, in the idealcase is eliminated or an abort criterion is reached. In other words,lower substrate holder 10 is moved back in a controlled, regulatedmanner to the already known, measured X-Y alignment position.

In a further embodiment, residual errors that are not eliminated in theposition of the upper and/or lower substrate can likewise be taken intoaccount as correction values for the positioning of the other (lower orrespectively upper) substrate.

Further correction factors can in particular be obtained from thevibrational state of the apparatus or parts of the apparatus asdescribed previously which, used for the positioning of the substrates,reduce the residual uncertainty of the positioning and increase thealignment accuracy. For the verification of the final position, all theknown interference factors and influences can again be taken intoaccount and correspondingly corrected.

Finally, in this process step according to the invention, movements ofsubstrate holders 10, 13 in an X-Y direction are prevented by clampingall the drives.

Once substrates 16, 17 have been aligned according to a method accordingto the invention, at least one of the substrates can be deformed in thedirection of the other substrate by means of a substrate deformationdevice 15, in order to join the substrates together with a pre-bond.

LIST OF REFERENCE NUMBERS

-   1 alignment apparatus-   2 optical system-   3 first/upper detection unit-   4 second/lower detection unit-   5 positioning device-   6 additional measurement system-   7 third/additional detection device-   8 positioning device of the additional measurement system-   9 frame-   10 first substrate holder-   10 a first fixing face-   11 first movement device-   12 common theoretical focal plane of the optical system-   13 second/upper substrate holder-   13 a second fixing face-   14 second movement device-   15 substrate deformation device-   16 lower substrate-   16 i first contact face-   16 o first support face-   17 upper substrate-   17 i second contact face-   17 o second support face-   20 first alignment marking-   21 second alignment marking-   22 third alignment marking

What is claimed is:
 1. A method for aligning and contacting a firstcontact face of a first substrate with a second contact face of a secondsubstrate, the method comprising: providing a first substrate having afirst contact face and a first support face, and a second substratehaving a second contact face and a second support face; fixing the firstsupport face of the first substrate on a first substrate holder and thesecond support face of the second substrate on a second substrateholder, said second substrate holder being arranged opposite the firstsubstrate holder; detecting a first X-Y position and/or a firstalignment orientation of a first alignment marking arranged on the firstsubstrate; detecting a second X-Y position and/or a second alignmentorientation of a second alignment marking arranged on the secondsubstrate; detecting a third X-Y position and/or a third alignmentorientation of a third alignment marking arranged on the first substrateholder and/or the first substrate; aligning the first substrate withrespect to the second substrate, comprising: correlating, in real-timeduring the aligning, the third X-Y position and/or the third alignmentorientation of said third alignment marking with at least one of (i) thefirst X-Y position and/or the first alignment orientation of said firstalignment marking and/or (ii) the second X-Y position and/or the secondalignment orientation of said second alignment marking; and controllingthe aligning of the first substrate with respect to the second substrateaccording to the real-time correlating; and contacting the firstsubstrate with the second substrate, said first substrate being alignedwith respect to the second substrate.
 2. The method according to claim1; wherein (i) the first alignment marking and the third alignmentmarking are respectively arranged on opposite sides of the firstsubstrate, or (ii) the first alignment marking is arranged on a side ofthe first substrate facing away from the first substrate holder and thethird alignment marking is arranged on a side of the first substrateholder facing away from the first substrate.
 3. The method according toclaim 1, wherein the first X-Y position is related to a focal plane of afirst detection unit.
 4. The method according to claim 1, wherein thefirst alignment marking is arranged on the first substrate at aperipheral region thereof.
 5. The method according to claim 1, whereinthe second X-Y position is related to a focal plane of a seconddetection unit.
 6. The method according to claim 1, wherein the secondalignment marking is arranged on the second substrate at a peripheralregion thereof.
 7. The method according to claim 1, wherein thedetecting of the first X-Y position and/or the first alignmentorientation of said first alignment marking and the detecting of thethird X-Y position and/or the third alignment orientation of said thirdalignment marking takes place simultaneously.
 8. The method according toclaim 7, wherein a first detection unit is used for the detecting of thefirst X-Y position and/or the first alignment orientation of said firstalignment marking and a third detection unit is used for the detectingof the third X-Y position and/or the third alignment orientation of saidthird alignment marking, wherein said first and third detection unitsare synchronized.
 9. The method according to claim 1, wherein the secondsubstrate holder is fixed at least in the X-Y direction during thealigning of the first substrate with respect to the second substrate.10. The method according to claim 1, wherein a first detection unit isused for the detecting of the first X-Y position and/or the firstalignment orientation of said first alignment marking and a seconddetection unit is used for the detecting of the second X-Y positionand/or the second alignment orientation of said second alignmentmarking, wherein said first and second detection units are provided on acommon X-Y positioning device and/or optical axes of the first detectionunit and of the second detection unit are aligned with or assigned toone another, having a common optical axis.
 11. The method according toclaim 10, wherein a third detection unit is used for the detecting ofthe third X-Y position and/or the third alignment orientation of saidthird alignment marking.
 12. The method according to claim 11, whereinthe third detection unit is arranged fixedly in the X- and Y-directionat least with respect to the first detection unit with respect to anoptical system comprising the first detection unit and the seconddetection unit, during the detecting of the third X-Y position and/orthe third alignment orientation of said third alignment marking, atleast until the aligning of the first substrate with respect to thesecond substrate.
 13. The method according to claim 1, wherein controlof the aligning of the first substrate with respect to the secondsubstrate takes place exclusively by means of the detecting of the thirdX-Y position and/or the third alignment orientation of said thirdalignment marking.
 14. The method according to claim 1, wherein thefirst substrate and the second substrate are arranged between the firstsubstrate holder and the second substrate holder with a constant spacingA between the first contact face and the second contact face in aZ-direction during the detecting of the first and second X-Y positionsand until the aligning of the first substrate with respect to the secondsubstrate.
 15. The method according to claim 14, wherein the spacing Ais less than 500 microns.
 16. A device for aligning and contacting afirst contact face of a first substrate with a second contact face of asecond substrate, said device comprising: a first substrate holder forfixing a first support face of the first substrate; a second substrateholder for fixing a second support face of the second substrate, saidsecond substrate holder arrangeable opposite the first substrate holder;a first detection unit for detecting a first X-Y position and/or a firstalignment orientation of a first alignment marking arranged on the firstsubstrate; a second detection unit for detecting a second X-Y positionand/or a second alignment orientation of a second alignment markingarranged on the second substrate; a third detection unit for detecting athird X-Y position and/or a third alignment orientation of a thirdalignment marking arranged on the first substrate holder and/or thefirst substrate; alignment means configured to align the first substratewith respect to the second substrate, the alignment means comprising:correlation means configured to correlate, in real-time during aligningof the first substrate with respect to the second substrate, the thirdX-Y position and/or the third alignment orientation of said thirdalignment marking with at least one of (i) the first X-Y position and/orthe first alignment orientation of said first alignment marking and/or(ii) the second X-Y position and/or the second alignment orientation ofsaid second alignment marking; and control means configured to controlthe aligning of the first substrate with respect to the second substrateaccording to the real-time correlating by the correlation means; andcontacting means for contacting the first substrate with the secondsubstrate, said first substrate being aligned with respect to the secondsubstrate.
 17. The device according to claim 16, wherein (i) the firstalignment marking and the third alignment marking are respectivelyarranged on opposite sides of the first substrate, or (ii) the firstalignment marking is arranged on a side of the first substrate facingaway from the first substrate holder and the third alignment marking isarranged on a side of the first substrate holder facing away from thefirst substrate.
 18. The device according to claim 16, wherein the firstdetection unit and the third detection unit are synchronised.
 19. Thedevice according to claim 16, wherein the second substrate holder isfixed at least in the X-Y direction during the aligning of the firstsubstrate with respect to the second substrate.
 20. The device accordingto claim 16, wherein the first detection unit and the second detectionunit are provided on a common X-Y positioning device and/or optical axesof the first detection unit and of the second detection unit are alignedwith and assigned to one another, having a common optical axis.
 21. Thedevice according to claim 16, wherein the third detection unit isarranged fixedly in the X- and Y-direction, at least with respect to thefirst detection unit, with respect to an optical system comprising thefirst detection unit and the second detection unit, during the detectingof the third X-Y position and/or the third alignment orientation of saidthird alignment marking, at least until the aligning of the firstsubstrate with respect to the second substrate.